Simatic Central Processing 6ES7318-3FL01-0AB0 6ES7 318-3FL01-0AB0 6ES7318-3FLO1-OABO

Siemens 6ES7318-3FL01-0AB0 | SIMATIC S7-300 CPU 319F-3 PN/DP — 2.5MB / MPI/DP + DP + PROFINET / Fail-Safe / Isochronous / Micro Memory Card Required

The Ceiling of the S7-300 CPU Range — and Why the "F" Matters

The CPU 319F-3 PN/DP sits at the top of the SIMATIC S7-300 CPU family. The "319" identifies the highest performance class in S7-300: 2.5MB of work memory — the largest in the range — with three independent communication interfaces covering MPI/DP, PROFIBUS DP master/slave, and integrated PROFINET in a single CPU module.

The "F" is the defining characteristic that separates this from the standard CPU 319-3 PN/DP. It designates a fail-safe CPU — one certified to execute safety programmes written with STEP 7 Safety Advanced and F-FBs alongside the standard user programme. The CPU 319F-3 PN/DP can implement Safety Instrumented Functions up to SIL 3 (IEC 61508) and PL e (ISO 13849) in combination with PROFIsafe F-peripherals on its PROFIBUS DP or PROFINET interfaces.

For machine and process applications where functional safety is part of the original design — not added with hardwired safety relays after the fact — the F-CPU is the controller that handles both the standard machine logic and the certified safety logic from the same module.

Key Specifications

Three Interfaces — Independent Communication Channels

The three-interface configuration is not redundancy for the same network — each serves a different communication purpose:

MPI/DP (1st interface): Programming terminal access, HMI connections via MPI, or PROFIBUS DP master/slave operation. In installations where the CPU 319F-3 connects to both an operator panel (over MPI) and a PROFIBUS DP field device network simultaneously, both connections use this single interface.

PROFIBUS DP (2nd interface): A second, independent PROFIBUS DP network. Separating field device groups across two DP networks — for example, drives on one segment and I/O stations on another — keeps unlike traffic profiles off the same bus and simplifies fault isolation.

PROFINET (3rd interface): Ethernet-based PROFINET IO, S7 communication over Ethernet, and SCADA/HMI connections via Ethernet. The integrated PROFINET port eliminates the need for a separate CP 343-1 communication processor module in the rack — saving a slot and reducing system complexity.

Isochronous Mode — Precision Timing for Motion Applications

Isochronous mode on the CPU 319F-3 PN/DP synchronises the PLC scan cycle to the PROFIBUS DP or PROFINET bus cycle in a phase-locked relationship. Every scan, input data is acquired at a precisely defined phase of the bus cycle, the programme executes, and outputs are transmitted at a precisely defined phase — all timed to the same clock source. For high-speed motion control, coordinated multi-axis applications, and precision measurement where data must be acquired at a reproducible machine cycle phase, this deterministic timing eliminates the variable-latency data acquisition of standard asynchronous operation.

FAQ

Q1: What does the "F" designation mean for CPU 319F-3 and how does it differ from the standard CPU 319-3?

The "F" identifies a fail-safe CPU capable of executing safety programmes using STEP 7 Safety Advanced and Siemens F-FBs. The safety programme runs in a protected F-runtime environment alongside the standard user programme, accessing PROFIsafe F-peripherals on the DP or PROFINET interfaces. The standard CPU 319-3 runs only standard programmes — it cannot execute certified safety logic. If the installed application includes a safety programme, the CPU 319F-3 is the required replacement; the non-F variant cannot substitute.

Q2: Does the integrated PROFINET replace the need for a CP 343-1 in the rack?

Yes. The CPU 319F-3 PN/DP's integrated PROFINET interface covers PROFINET IO controller operation, S7 communication over Ethernet, and HMI connections via Ethernet — the same functions a CP 343-1 would provide. An additional CP 343-1 is not required for the standard PROFINET communication needs of a CPU 319F-3 installation. This frees a rack slot compared to the CPU 319-3 (no built-in PROFINET) + CP 343-1 combination.

Q3: What Micro Memory Card capacity is required?

The capacity depends on the programme size. Siemens Micro Memory Cards for S7-300 are available in 64KB, 128KB, 512KB, 2MB, and 4MB capacities. For the CPU 319F-3 with 2.5MB work memory and a full safety programme alongside the standard programme, a 4MB MMC is the appropriate specification in most configurations. Confirm the required capacity from the installed system's STEP 7 project backup before sourcing the card.

Q4: Can isochronous mode be used on both PROFIBUS DP and PROFINET simultaneously?

The isochronous mode clock is derived from the selected synchronising interface — PROFIBUS DP or PROFINET. Both interfaces cannot be isochronous masters simultaneously in the standard configuration; one interface provides the clock source for the synchronised cycle. The standard OB61 organisation block framework in STEP 7 manages the isochronous scan execution relative to the selected interface's cycle.

Q5: Where is the 6ES7318-3FL01-0AB0 sourced?

As a Siemens spare part, through Siemens service channels (Siemens Industry Mall, service centres) and the established S7-300 CPU aftermarket — industrial automation spare parts dealers and tested surplus suppliers. The CPU 319F designation (fail-safe) is a specific certification class; confirm the F designation from the installed unit's label before accepting a replacement. A standard CPU 319-3 cannot substitute in a safety application.